1. Field of The Invention
The present invention relates to a vehicle door locking apparatus and a control method therefor.
2. Description of The Prior Art
Hitherto, there has been publicly known a door locking apparatus which has a lock lever displaceable between a locking position and an unlocking position by operating a key cylinder provided on the outside of a door or an inside locking button provided on the inside thereof, and an anti-theft mechanism or a super-lock mechanism for disabling the lock lever from being displaced from the locking position to the unlocking position by operating the locking button.
FIG. 12 schematically illustrates a door locking apparatus with an anti-theft mechanism proposed in the U.S. Pat. No. 4,978,154. This door locking apparatus has a lock lever A for changing the state of the apparatus between a locked state and an unlocked state, and a switching body B which can slide laterally from a shaft C and has a projection D at a left end thereof. FIG. 12 shows the switching body B which has been slid rightwardly from the shaft. Thus, the projection D engages with a fork portion E of the lock lever A. The locking apparatus is further provided with a lever H having an elongated hole I with which the projection D engages. A rocking motion of the lever H causes the switching body B to slide from side to side. A top or nut L is screwed on a threaded spindle K which is rotated by a motor J. An outer cylinder M engaging with the lock lever A is engaged with the outer surface of the top L through a lost-motion coupling.
FIG. 12 illustrates a locked state in which the inner top L and the outer cylinder M are leftwardly moved through the rotation of the motor J up to the locking position. In this state, an inside locking button G is coupled to the lock lever A by engaging the projection D of the switching body B with the fork member E of the lock lever A. Thus, the lock lever A can be switched between the locking position and the unlocking position by using the inside locking button G. When the motor is further rotated from the state or position of FIG. 12, the outer cylinder M does not move but the top L singly moves to the left to thereby turn the lever H counterclockwise. Consequently, the switching body B is moved leftwardly. Further, the projection D is disengaged from the fork portion E. Thus the coupling between the inside locking button G and the lock lever A is canceled. This is anti-theft state.
When changing the state of the aforementioned known locking apparatus into the locked state from the unlocking state, the top L should be stopped at the locking position. Thus, if the top L goes beyond the locking position to the left, the state of the locking apparatus is changed into the anti-theft state. Therefore, the locking apparatus is constructed in such a manner that the rotation of the motor is stopped in response to a signal from a sensor N which can detect the locking position of the top L or the cylinder M when the top L or the cylinder M reaches the locking position.
However, even if is stopped energizing the motor J in response to a signal from the sensor N, the motor J turns to no small extent owing to the inertia. Therefore, it becomes very difficult to securely stop the top L at the locking position. Thus, a countermeasure against the excessive rotation of the motor J due to the inertia (for example, a change of the mounting position at which the sensor N is mounted on the locking apparatus) is applied to the locking apparatus. This countermeasure is not very effective, because variations in resistance value of components and in voltage provided by a battery serving as a power supply for the motor J cause a large variation in amount of rotation of the motor J in the case of mass-produced locking apparatuses.